1. Field of the Invention
Embodiments of the present invention generally relate to touchdown detection in a hard drive. And, more specifically, to touchdown detection in a head of a hard drive with multiple touchdown sensors located at an air bearing surface (ABS).
2. Description of the Related Art
Disk drives typically use heads residing on sliders to read from and write to the magnetic media. Read and write transducers residing in the head are flown at a small, controlled spacing above the magnetic medium during read and write operations. Although it is generally desired to operate the head only in close proximity to the disk, the head may contact the magnetic medium. A prolonged contact—e.g., on the order of tens of microseconds or more—is known as a touchdown. Heads typically use a thermal actuator that generates heat to control the head-to-media spacing. Heat generated by the thermal actuator causes thermal expansion of the head which locally reduces the spacing between the head and magnetic media. The thermal actuator can produce heating sufficient enough to cause contact between the head and media—i.e., a touchdown event. This touchdown is intentional and is generally performed on each drive during initial drive calibration. Touchdown may also occur at other times during disk drive operation, for example, due to changes in environmental conditions, operation of the disk drive outside of desired parameters, or contamination of the head or magnetic medium. It may be desirable to accurately detect touchdown in order to limit contact time between the head and disk. Prolonged contact is generally undesirable as it may lead to drive failure.
Accordingly, what is needed is a system and method for providing improved touchdown detection.